I have a small edge case. I want to tighten down my servers as much as possible while remaining their given functionality.
I have UFW enabled with the current default rules:
Deny all incoming - Deny all outgoing
On top of this, I have given my configuration management tool access to SSH on a non-standard port. I have enabled HTTP and HTTPS so that it can talk to the web, I've enabled FTP so that it can receive files, I've enabled DNS so that it can resolve domains.
Still, I'm unable to curl any sites, unable to use apt-get and update. I can use it fine and can SSH into it with my management tool, but I'm unable to do anything else.